Cancer diagnoses occur within a milieu of pre-existing and evolving co-morbidity. In a population-based, three-year longitudinal survey database linked to Medicare claims (the Prevention of Secondary Conditions Study database), we have studied the inter-relationship of pre-existing co-morbidity, evolving co-morbidity (also termed "secondary conditions"), and the trajectory of functional status. The purpose of this pilot project is to determine whether individuals aging with a history of cancer have a greater progression in mobility disablement and to evaluate the extent to which this is explained by pre-existing co-morbidity and the development of secondary conditions. Primary aims focus on the long-term progression of mobility disability and quality of life among cohort members with a history of cancer at baseline, specifically to: 1) determine whether cancer survivors (those with a history of cancer at the baseline survey) are more likely to experience progression of mobility disability and decrement in quality of life than people without cancer, controlling for baseline number of mobility limitations and co-morbidity; 2) determine whether development of secondary impairments explains long-term progression of mobility disability and decline in quality of life after cancer diagnosis; and 3) among people with a history of cancer, describe risk factors for developing secondary impairments, including: cancer characteristics (cancer site, extent of disease, time since diagnosis, and original and current treatment modalities), individual co-morbid conditions, number of co-morbid conditions, baseline medications, mental health summary score, physical health summary score, social support, barriers to health-promoting activities, perceived access to care, and geographic access to care.